- So you can watch amazing isolated examplesof how iZotope RX modulescan seamlessly fix audio problems.But in your own experience and with your own files,before you fix anything,you have to first learn how to identifywhat the problem is,before you can start repairing it with the modules.In this movie we'll discuss how to identifycommon audio problems,and we'll explore iZotope's suggested flowcharton what order to solve the issues with.Now to see a comprehensive range of problemsyou might encounter,I prepared this rxdoc with a bunch of samples.

Notice I made the use of markersacross the top of the screen here.These are examples of selection based markers,and you can make any marker of your own.If you wanna make a single markeryou can just click in anywhere in the timeline,open up the Markers and Regions windowand here we can see all the markersI've already made.But if I wanted to add a marker,say at this location,I can click Add,and then I can name the marker.

I can also make a selection based markerby creating a selection,and thenclicking Add,and then I can make a selection based markerthat will stay there.And as you see,you can add comments or anything elsethat you might want to add that will show upin the Markers and Regions window.Now to remove these I can just select themand remove them.The other cool thing about theMarker and Regions window is that I can jumpto any marker by clicking on the little yellow icon.

So if I wanna go to the Clicks and Pops selection,I click there and it automatically selects the audio,and then I can play that audio.- Ladies and Gentleman.- I can also click just on the little trianglewhich is basically a play button,and it'll play from that location.- Blast of. Blast off. Blast off. Blast.In this case it's looping,because I have the loop button turned on.So that's how markers work,and again I've made a whole bunch of markersacross the timeline so we can quickly jumpto these all examples of audio problemswe might encounter,and we'll talk about what moduleswe might want to use to address these problems.

So let's start at the first one,it's called Clipped.And I can zoom in a little bit on that selection,over here on the left,I have clipped audio.Clipped audio is the name of audiowhich has overloaded the input of a mic,a recording device,an interface, etcetera.If you digitally clip,or you overload the input,what happens is the waveformsget basically squared off.And if we zoom in a little more,we can see the top part of these waveformshas been chopped off,and that's essentially why we call it clipped.

And here's what it sounds like.- Welcome to kiapics.com,the number one image hosting site on the web.- So over here, it's not clipped.The first part is clipped,and you can heara kind of crunchy character to that audio.- Welcome to kiapics.com.- Now luckily we can fix this really easilywith a module called Declip.So, if I open this up,we can see the Declip moduleand it'll essentially find where the audio is clipped,and restore it.Now, don't worry,we're gonna go into how to use all these modulesas we progress in this course.

For now, I want to concentrate just on identifyingthe problems and talking about which moduleswe'll use to solve the problem.So let's move on.Let's go to the next example I have,which is called Distortion.And I'll zoom out,and I'll zoom back in on the Distortion section.So now, distortion at first might sound like clipping,but if you look at the waveforms,you don't see any clipped waveforms.What we do hear is some distortion,and let me play it for you.

- Blast off. Blast off.- So that doesn't sound perfectly natural,it sounds like there's some kind of build upof frequencies going on within the spectrum.Now to fix this,there's a couple of modules you can turn to.If you're an advanced user,you can use the Deconstruct modulewhich lets you actually reduce Noisy gainversus Tonal gain,which can help extractsome of that frequency build up.If you don't have iZotope RX 4 Advanced,you can use Spectral Repair to look atand analyze the audioand find where those frequency build ups areand lower the volume of the frequency build upsto make a distorted passage a little bit more natural.

Okay so, moving on,we've got Clicks and Pops.This is pretty obvious in terms of the name.Let me just play it for you,and we can hear some clicks and pops.- Ladies and gentlemen,we are approaching Mars' lower orbit.Fasten your seat belts and prepare yourselffor atmospheric reentrance.- Now, you heard those little clicksand digital glitches in there.Digital clicks and pops like thiscan be caused by digital clocking errorsfrom a digital recording devicethat's something's wrong going on,bad sample rate perhaps,it's not synced to another device.

It can happen if you have bad digital cabling.It can also happen in the analog worldif you're working with audio from vinyl records,for example.You're gonna have some clicks and popsbecause of the dust and possibly scratchesof the vinyl records.Luckily, to fix any kind of clicks and pops like this,we have a Declick module.And the Declick module,let me just return it to it's default setting,has three tabs.Declick, Decrackle, and Interpolate.And a combination of one or more of these tabs,can really help isolate and take careof a lot of the clicks and pops we might encounter.

Okay, moving on,I have an example called Crackle and Mouth Noise.Now if you've recorded any VO recording,or any close-up vocal performances,you might be familiar with mouth noisethat you can hear in that recording.Let me play an example for you.- Finally, click the upload buttonand you're ready to share your imagewith the world.Finally, click the upload buttonand you're ready to share your imagewith the world.- Okay it sounds pretty good,but we do hear a lot of that sort ofclicky, crackly mouth noise,and we could make this a lot cleaner.

And we would do that by using alsothe Declick module,specifically the Decrackle tab of the Declick modulewill help us take care ofany kind of mouth noise problems like this.Okay moving on,I have an example called Amp Hum.Now hum is a specific kind of audio problemwhere you have a continuous tonerunning throughout your audio,and there's a couple of characterizations of it.In the first example here called Amp Hum,it's a guitar playing through an amp.

And if you've ever recorded amps before,you've definitely heard that they can havesome audible hum.Let's take a listen.(electric guitar)So hum can come through cables electrically,or it can just be present in a room if,for example you forgot to turnthe refrigerator off.It can be heard audibly as a low frequency tone,and it's usually based at either 50hz or 60hz,depending on whether the recording was madein Europe or North America,because of the different way the electricity worksin both places.

Here in this example,it's related with an electric guitar amp,and it's at 60hz.And you can see though visually,the bending across the bottomof the spectral readout of this clipthat it actually occurs below the usable audio signalof the guitar,which is happening above that area.So for situations like this,the Remove Hum module works really well.You can basically give it a base frequencyand we can add in basically EQ filtersthat have very tight response curvesto deal with some of these problems.

And it's a very effective way to get rid of hum,like we're seeing here.But the other type of hum that we might encounter,I've name In Spectrum Hum.So let's take a listen to this,and see what the difference is.- Fasten your seat beats and prepare yourselffor atmospheric reentrance.- So this clip also has a hum,but you can see visually that the bands of the humextend well up into the areawhere the voice is.So for this type of audio problem wherethe hum is sharing frequencieswith the audio you want to keep,you probably won't have a ton of luckwith the Remove Hum.

For this type of audio problem,you'd want to turn to the Denoise module.And the Denoise module,if you can get an isolated example of the hum,you can learn the hum and then you can workto remove it from the areawhere the voice is,where the frequencies of the voice arewithout altering the voice.So that might be a better way to dealwith that kind of problem.Okay next we have an all too familiar situation.I'll just play it for you and you can hear it for yourself.

- 10.Nine.Eight.Seven.Six.- Yes it's cell phone interference,so if you have a cell phone too closeto the recording device,you can get some intermittent blips and bleepsinto the recording like we have here.Luckily for this type of problem,we can actually use a preset in the Declick module.If you go up here to Presets,there's actually one specifically designedfor this type of problem.And that'll take care of most of the problem,and then the rest of the cell phone clicks and buzzescan be taken care of with the Spectral Repair module.

Okay, the next selection is somethingwe call broadband noise.This is what happenswhen you've got noise problems,not hum based noise problems,but just broadband,meaning they're happening acrossall of the frequency spectrum.Something like an air conditioning or a fanis a good example of broadband noise.Let's take a listen.- Fasten your seat belts and prepare yourselffor atmospheric reentrance.- That air conditioning unitthat we hear in that recordingmight have some hum components,which you can see banding across,but you can also see that the noise problems extendas just broad sort of,scattering of frequenciesthat exist all up into the audio spectrum.

Now to take care of this kind of noise,we'd also turn to the Denoise module,and we can try the Spectral Denoise.There's also one tab of the Denoise modulethat's specifically made for dialogue based denoising.So that might be a good opportunitysince this is dialogue,it's someone speaking,we can try out in this case the Dialogue Denoiser.Okay, our next example issomething we call intermittent noise problems,so take a listen.- Everything that I look for in life,from family to--- Just move this. - everything that Ilook for in life. - So hereI'm gonna zoom in a little bit.

The voice sounds okaybut you can hear intermittent noise problems.Which in this case,come as the sound of birds.- Everything that I look for in life, from family.- And you can actually see where the birds occur,occurring here and here,and watch those areas as we play it.- Everything that I look for in life,from family to.- So anytime you have this kindof intermittent problem,maybe it's a chair squeak,maybe it's someone coughing in the background,or in this case, birds.You can deal with these with the all powerfulSpectral Repair module,and you can actually select those areasand work to either Attenuate,Replace,or Pattern replacethose types of problems very effectively.

And that's one of the most powerful modulesin iZotope as we'll come to see.Okay the next problem we have,is called Dropout.Dropout is characterized by short periodsof missing audio.Dropouts can be the result of a digital glitch,a bad RF,bad radio frequency from wireless lavaliers,that's a really common place you might have dropout.Even bad tape in the analog world.So let me play this and we can seewhere the dropout occurs.- Ladies and gentlemen,we are approaching Mars' lower orbit.

- Okay so right there,I zoom in really close,right where he says Mars' lower orbit.- Mars' lower orbit.- Okay, so you see there's a missing chunkof audio right there.That would be a dropout.We can also deal with dropoutsby using the Spectral Repair module.And here we can use either Replaceor Pattern to find and isolate audiothat's like this missing area,and interpolate and fill in that area.

And for our last example,we have a recording with too much reverb.Now usually people think of reverb as a good thing,but let me play this exampleand you can hear when we might not want reverb.- Too much sugar dehydrates you,and robs your energy when you need it most.- So the space of this recording is interferingwith the intelligibility and even the moodof the recording.And removing reverb from an audio clip like this,is kind of like a holy grail of audio restoration.It's maybe the hardest thingto fully remove from audio,since the room or the surroundingswe want to remove are so blended inwith the audio we want to keep.

For this type of problem,RX 4 Advanced users can turn tothe Dereverb module,which basically analyzes a clip of audio like this,and finds out where it can sort of get rid of,or dock the reflections,the unwanted reverb.It's a very powerful toolpart of the RX 4 Advanced Suite.So that's a pretty comprehensive listof audio problems you might encounter in the world.But many recordings have more than oneof these issues going on.So in that case,where do we start,and what order do we process the problems in?Luckily iZotope in some of their documentationmade a very handy flowchart of how to diagnoseand what order to diagnose issues in.

So here is a flowchart,a sequence of steps,questions you can ask yourself basically,as you go through.The flowchart starts with the question, Clipping,and know we know what clipping is, right?So is it clipping?And the way this works is,if it is clipping,you would go to these modules.Start with the Declip module.If that doesn't work,go to Decrackle.If that doesn't work,go to Deconstruct.So you can follow this flowchart around,and you just basically ask yourselves the question.Is clipping your problem?If not, go on.If stereo file with stereo noise clicksis not the problem,you go on.

And so basically this gives you a really nice flowchartwith sort of suggested order and wayto diagnose audio problems.A very handy thing,you might want to print it out,and keep it next to your work stationif you're doing a lot of work in RX 4.So even though we've identified specific modulesfor specific problems,I want to point out,that even with all this technology,there is no one-click magic button or silver bulletthat will fix all the problems with your audio.You can use these modules,but use of them requires very exactand skillful selection techniques.

That it requires accurate settings,and this is the main part,a lot of trial and error on your partto make even small improvements.So there, I said it.iZotope RX can help repair your audioand make it better.There's no application under the sunthat can fix everything perfectly all the time.It's gonna require you to use a lotof your listening skills and a fair amount of timeto try things,undo them,compare things,try some modules against other modulesand see which one works better, etcetera.

So right now I'm working on a time machinethat allows usto go back to the date and locationof recordings when they were made,and do things like turn off the refrigeratoror dampen the room,so it's not so reflective.But until I get that done,iZotope is the best tool we haveto deal with some of these audio problemswe're going to encounter in our recordings.

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Author

Released

5/8/2015

Explore the noise reduction and audio restoration possibilities—for both music and post production—in iZotope RX 4 and RX 4 Advanced. Author Scott Hirsch covers all of the best and latest features of RX 4, demonstrating techniques for fixing audio problems in a variety of situations. He'll show how to reduce noise, connect with a DAW such as Pro Tools or Logic Pro, and use advanced features such as EQ Match, Ambience Match, and the utility modules for resampling, retiming, and pitching audio.